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Jim Grant's Tech Tips
'00 Ford Contour SE, High Speed Stalling
Q:
I recently purchased a 2000 Ford Contour SE (now at 40k). Within a month
of the purchase, the car began to sputter when pressing the accelerator
at highway speeds (60-70mph). At one point, the engine stalled. The only
difference on that occasion was that the defroster was running. After
pulling over, the car immediately started again and I was able to get
home. There have been no further stalls, only power fluctuations when
accelerating at high speed. A mechanic read the codes and pending codes,
which indicated a problem in the fuel system, but they were not specific.
Rather than replace expensive parts, he suggested I drive it further until
the problem happens again. I am considering buying an Autotap to monitor
the OBDII data the car is providing, but do not know what to look for
(fuel pressure/mixture, etc...). Any suggestions on repairs to look at
or OBDII data to examine would be very helpful. With the tap, I will be
able to monitor the data at highway speed, which I do not think the mechanic
did......Ryan
A:
I’m
not familiar with the Autotap but if it is a data reader (computer scan
tool of sorts) it is a tool to provide direction in solving your problem.
The data that I would watch for first would be of the oxygen sensor. Because
your vehicle has 2 sensors the one you want to watch is sensor # 1. Sensor
#1 is the first sensor the exhaust passes over. Sensor #2 is after the
converter. The #2 sensor is primarily used by the computer for converter
efficiency monitoring. The value displayed will be in millivolts (mv)
and will range from .000 to a high of about .999. That is the range only,
in reality it will be between .100 to .900 . The next question is how
can these numbers help diagnose your problem? It’s simple, really.
Any number displayed over .450 mv means there is enough fuel. A number
displayed under .450 mv means there’s not enough. When watching the
oxygen sensor data you will notice that the numbers go up and down (above
and below .450 mv) at a fairly quick rate. This is a good thing. It means
the computer is working correctly. It’s when the number stops switching
is when there is a problem. If the voltage readings of the O2 sensor drop
that means (in most cases) there is not enough fuel. Sort of like running
out of gas. From your description it is likely that you’ll see the
O2 sensor voltage drop when the vehicle is acting up. If this is the case,
then there may be a fuel supply problem. One word of warning. Watching
a vehicle’s computer data can be dangerous. Why? Let’s put it
this way. On more than one occasion a tech has driven into something while
watching the computer information and not the road. So scan with care
or get a co-pilot!
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